The invention relates to a mounting apparatus for an optical element and more particularly to a mounting apparatus for mounting a lens.
Optical elements, e.g. lenses, have to be installed and adjusted very precisely in relation to their mechanical reference, in particular, in lens systems for semiconductor lithography. It is thus the case, eg. with lenses, that the optical axis has to be made to coincide as precisely as possible with the ideal mechanical axis.
The Applicant""s earlier application P 199 08 554.4 discloses a three-point mounting via solid-state rotary articulations with solid-state transitions which can be adjusted by manipulators. A three-point mounting is also known from U.S. Pat. No. 3,917,385.
The object of the present invention is to improve the hitherto known installation and adjustment mounting method by an integrated fine-tuning functional unit, in order to achieve higher positioning accuracy.
Methods and apparatuses for achieving this object are described. In one embodiment, a mounting apparatus for an optical element includes an inner mount and an outer mount, the inner mount being connected to the outer mount via three circumferentially distributed articulations. An exemplary mounting apparatus is disclosed in U.S. Pat. No. 6,580,570, issued Jun. 17, 2003, to Becker et al., which is incorporated herein by reference. Manipulators act on the articulations wherein said inner mount is displaceable, and wherein the articulations comprise a mechanism which transforms a radial movement into an axial movement. In another embodiment, the mounting apparatus is for mounting a lens in a projection lens system for semiconductor lithography. In another embodiment, the articulations comprise at least one lever for transforming the radial movement into an axial movement, wherein the manipulators act on said at least one lever. In another embodiment, the articulations comprise at least one bell crank lever with attachment points between the inner mount and the outer mount. The outer mount is located in the region of the outer ends of a first lever of the at least one bell crank lever and the manipulators act in the region of the outer end of a second lever of the at least one bell crank lever which is in an angle to the first lever.
In another embodiment, the articulations comprise at least one T-shaped lever in cross section, with a T-bar and a T-support, attachment points between the inner mount and the outer mount being located in each case in the region of the outer ends of the T-bar, and the manipulators acting on the T-support in each case, this embodiment being disclosed in U.S. Pat. No. 6,580,570, previously incorporated herein by reference.